CN115172705B - Secondary battery and electricity utilization device - Google Patents
Secondary battery and electricity utilization device Download PDFInfo
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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Abstract
The invention provides a secondary battery, which comprises a positive plate, a negative plate and a diaphragm which is arranged between the positive plate and the negative plate, wherein the negative plate comprises a negative active substance, the negative active substance comprises a silicon oxide material and a carbon-based material, the mass percentage of the silicon oxide material in the negative active substance is a, a is more than or equal to 3% and less than 100%, the discharge depth of the secondary battery is S, and the S and a satisfy the relation: s=1.015-0.5244a+0.4717a 2 . Compared with the prior art, the secondary battery provided by the invention has the advantages that the mixing proportion of the silicon oxygen material is used to satisfy S=1.015-0.5244a+0.4717a 2 The discharging depth of the secondary battery is determined, so that the discharge capacity is maximized on the premise that the swelling and cracking degree of the silicon oxide material particles is minimized in the charging and discharging process, and the cycle performance of the battery is guaranteed to be optimal.
Description
Technical Field
The invention relates to the field of secondary batteries, in particular to a secondary battery and an electric device.
Background
The new energy automobile is an industry which is greatly developed in the future automobile industry. The secondary battery is widely applied to the new energy automobile industry because of the advantages of high energy density, no memory effect, long service life and the like. However, as the demand for new energy vehicles increases, a higher energy density is required for distribution to the batteries. Therefore, development of a new positive and negative electrode material for lithium ion batteries is urgently required, and a graphite-based negative electrode is currently used as a common negative electrode material in the market. The theoretical gram capacity of graphite is 372mAh/g, and with the increasing maturity of industrial technology, the current high-end graphite can reach 360-365mAh/g and is very close to the theoretical capacity. However, the energy density limited by the material itself to 280Wh/kg has been nearly limited, and it is difficult to meet the increasing demand for higher energy density. The theoretical gram capacity of the silicon material is 4200mAh/g, and the lithium-removing potential is relatively low (0.4V), the silicon material is environment-friendly, and the resources are rich, so that the silicon material is considered to be a potential cathode material of a next-generation high-energy-density lithium ion battery.
Many manufacturers have begun to use a blend of silicon oxide (SiO) and graphite as the negative electrode material for high energy density lithium ion batteries. However, silicon-based cathodes also have many problems during use, mainly due to the problem of volume expansion of silicon. The volume expansion of the simple substance silicon after lithium is fully intercalated is more than 300%, the expansion of SiO is improved, but the expansion is also up to 180%, and then the particles are pulverized due to the huge stress caused by huge volume deformation in the repeated lithium intercalation and deintercalation process; electrical contact is lost between particles or between particles and a current collector, and even active substances are directly separated from the current collector; the silicon surface SEI is continuously broken and generated, consuming a lot of electrolyte and active lithium, and also increasing the battery polarization.
Various solutions for the self direction of materials such as nano silicon, carbon coating, metal doping, core-shell structure and the like are proposed for improving the problems, and meanwhile, the solution is matched with a conductive agent, an electrolyte, a binder and the like in the system direction. While the expansion of the silicon-based material is reduced, the expansion is still greater for the cell. The end result is a significant decrease in cell performance, such as cycle life, with increased silicon content, although the cell energy density is increased compared to pure graphite systems.
In view of the foregoing, it is necessary to provide a solution to the above-mentioned problems.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the secondary battery can effectively prolong the cycle life of the battery on the premise of ensuring the maximum exertion of the energy density of the silicon-based secondary battery.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a secondary battery comprises a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, wherein the diaphragm is formed by a metal plateThe negative electrode sheet comprises a negative electrode active material, the negative electrode active material comprises a silicon oxide material and a carbon-based material, the mass percentage of the silicon oxide material in the negative electrode active material is a, a is more than or equal to 3% and less than 100%, the discharge depth of the secondary battery is S, and the S and a satisfy the relation: s=1.015-0.5244a+0.4717a 2 。
Preferably, the secondary battery is fully charged at 0.05 to 3C and then discharged to S at 0.05 to 3C.
Preferably, a is more than or equal to 3% and less than or equal to 80%.
Preferably, the silicon oxide material is SiO x Lithium-containing SiO x SiO containing magnesium x X is more than 0 and less than or equal to 2; wherein the SiO contains lithium x The mass ratio of the lithium in the alloy is 0 to 15 percent, and SiO containing magnesium x The mass ratio of the magnesium is 0-15%.
Preferably, the particle diameter D10 of the silica material is 1-5 mu m, and the D50 is 4-15 mu m; the specific surface area of the silicon oxide material is 0.8-3.5 m 2 /g。
Preferably, the particle size concentration N of the silica material is 0.01-2.
Preferably, the mass percentage of the carbon-based material in the anode active material is b, and b is more than or equal to 20% and less than or equal to 95%.
Preferably, the carbon-based material is at least one of artificial graphite, natural graphite, hard carbon, graphene and soft carbon.
Preferably, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on at least one surface of the negative electrode current collector, the negative electrode active material is arranged on the negative electrode active material layer, the negative electrode active material layer further comprises a binder and a conductive agent, and the mass ratio of the negative electrode active material to the binder to the conductive agent is (90-96): (2-5): (1-5).
Another object of the present invention is to provide an electric device including the secondary battery according to any one of the above.
Compared with the prior art, the invention has the beneficial effects that: the invention provides a secondary battery, wherein the negative electrode active material adopts silicon oxygen material andcarbon-based material, and the present inventors satisfied that s=1.015 to 0.5244a+0.4717a by using the mixing ratio of the silicon oxygen material 2 And determining the depth of discharge of the secondary battery, so that the discharge capacity is maximized on the premise of minimizing the swelling and cracking degree of the silicon oxide material particles in the charge and discharge process, and the cycle performance of the battery is ensured to be optimal, namely the cycle life of the battery can be effectively prolonged on the premise of ensuring the maximization of the energy density of the silicon-based secondary battery.
Detailed Description
The first aspect of the present invention aims to provide a secondary battery comprising a positive electrode sheet, a negative electrode sheet and a separator interposed between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode active material comprising a silicon oxide material and a carbon-based material, the silicon oxide material is present in the negative electrode active material in a mass percentage of a, a is 3% or more and less than 100%, the secondary battery has a depth of discharge of S, S and a satisfying the relation: s=1.015-0.5244a+0.4717a 2 。
The depth of discharge (Depth ofdischarge, doD) is a percentage of the discharge capacity of the battery to the rated capacity of the battery, i.e., the current state of charge of the battery. For example, the depth of discharge is 80%, that is, the discharge is to the remaining 20% of capacity. For example, the depth of discharge is 60%, that is, the discharge has a capacity of 40%.
The silicon oxide material has the problem of larger volume expansion in the charging and discharging process, and a series of adverse reactions such as particle pulverization, material dropping, continuous cracking and generation of SEI films and further consumption of a large amount of electrolyte can be generated in the charging and discharging process, so that the performances of the battery such as circulation and the like are poor. In general, reducing the charge-discharge capacity interval (i.e., the depth of discharge) can slow down the adverse reaction of the silicon oxide material, improve the cycle performance, and increase the service life of the battery. However, the charge-discharge capacity interval (i.e., the depth of discharge) is positively correlated with the discharge capacity, and the larger the depth of discharge, the larger the discharge capacity, and vice versa. If the charge-discharge capacity interval is too narrow, the capacity of the silicon oxide material cannot be effectively utilized, the advantages of the silicon oxide material cannot be reflected, and the energy density of the battery is reduced. If the charge-discharge capacity interval is too wide, adverse reactions such as particle pulverization and the like can be caused in the charge-discharge process, so that the cycle performance and the service life of the battery are reduced.
The inventors found that when s=1.015-0.5244a+0.4717a is satisfied 2 Under the condition that the mixing proportion of the silicon oxide material corresponds to a specific discharge depth, the discharge capacity can be maximized on the premise that the swelling and cracking degree of silicon oxide particles is minimized in the charging and discharging process, and meanwhile, the cycle performance is optimal, so that the composite silicon-based secondary battery with high energy density and long cycle performance is provided.
Specifically, the a may be 3% or less than 5%, 5% or less than 10%, 10% or less than 15%, 15% or less than 20%, 20% or less than 25%, 25% or less than 30%, 30% or less than 35%, 35% or less than 40%, 40% or less than 45%, 45% or less than 50%, 50% or less than 55%, 55% or less than 60%, 60% or less than 65%, 65% or less than 70%, 75% or less than 80%, 80% or less than 85%, 85% or less than 90%, and 90% or less than 100%. Preferably, a is 3% or more and 80% or less. More preferably, a is 5% or more and 50% or less. Further preferably, a is 5% or more and 40% or less.
In general, the larger the ratio of a, the larger the theoretical capacity of the corresponding secondary battery, but at the same time means that the more severe the swelling fracture of the silicone particles, the improvement in cycle performance is relatively speaking even if the relational expression is satisfied. For secondary batteries that do not satisfy the above-described relation, as a increases, the degree of opposition of the battery energy density to the cycle performance increases; and for the secondary battery meeting the relation, the secondary battery can ensure the maximization of the battery energy density under the a proportion on the premise of the same a blending, and simultaneously ensure the optimal cycle performance under the a proportion. In addition, the advantages of the relation of the invention are more obvious as a increases in a certain range.
In some embodiments, the secondary battery is discharged to a depth of 0.05-3C for full charge and then 0.05-3C for discharge to S. Preferably, the full charge is performed at 0.05-1C, and then the discharge is performed at 0.5-2C until the discharge reaches S. More preferably, the battery is fully charged at 0.5C and then discharged to S at 1C, the relation between the depth of discharge and a under the condition is controlled, the maximization of the battery energy density exertion under the a proportion can be further ensured, and the optimal cycle performance under the a proportion is ensured.
In some embodiments, the silicon oxygen material is SiO x Lithium-containing SiO x SiO containing magnesium x X is more than 0 and less than or equal to 2; wherein the SiO contains lithium x The mass ratio of the lithium in the alloy is 0 to 15 percent, and SiO containing magnesium x The mass ratio of the magnesium is 0-15%. SiO as described above x Can be SiO or SiO 2 。
The lithium-containing SiO x Namely, the pre-lithiated silicon-based negative electrode material, since the silicon-based material consumes a large amount of lithium to form an SEI film in the first charging process, the first cycle efficiency of the battery is reduced, and the removable lithium is reduced. By prelithiation of the silicon-based material, i.e., lithium is replenished at the material end, the subsequent SEI film formation consumes the lithium, thereby improving the initial efficiency of the battery. Likewise in SiO x The magnesium-containing silicon-based battery can also play a role in improving the first cycle efficiency of the silicon-based battery, and can improve the expansion and conductivity of the battery to a certain extent. Preferably, lithium-containing SiO x The mass ratio of the lithium in the lithium ion battery is 0.1-8%; siO containing magnesium x The mass ratio of the magnesium is 0.1-8%.
In some embodiments, the silica material has a particle size D10 of 1 to 5 μm and a D50 of 4 to 15 μm; the specific surface area of the silicon oxide material is 0.8-3.5 m 2 And/g. The particle size and specific surface area of the silica material are controlled within the above ranges, the silica material has relatively low volume expansion, the discharge depth S of the secondary battery is synchronously controlled, the pulverization degree of silica particles can be further reduced, and the energy density and the cycle life are ensured.
In some embodiments, the silica material has a particle size concentration N of 0.01 to 2. Wherein, the particle size concentration N= (D90-D10)/(D50). The particle size concentration is preferably 0.5 to 1.5, and specifically may be 0.5 to 0.6, 0.6 to 0.7, 0.7 to 0.8, 0.8 to 0.9, 0.9 to 1.0, 1.0 to 1.1, 1.1 to 1.2, 1.2 to 1.3, 1.3 to 1.4, or 1.4 to 1.5. The concentration of the particle size is controlled, the size distribution of the silica particles is more uniform, the controllability of volume expansion is higher, the discharge depth S of the secondary battery is synchronously controlled, more capacity can be further released, and meanwhile, the secondary battery has better cycle performance.
Wherein the particle diameter D50 means that particles smaller than this particle diameter account for 50% of the whole. Particle size D10 means that particles smaller than this particle size account for 10% of the total. Particle size D90 means that particles smaller than this account for 90% of the total. D10, D50 and D90 of each material can be determined and screened by methods known in the art, for example by laser particle size analysis, with screens of different mesh numbers.
In some embodiments, the mass percentage of the carbon-based material in the negative electrode active material is b,20% or more and 95% or less. The negative electrode active material is mainly a mixture of a silicon oxide material and a carbon-based material, and the other materials can be doped materials or only comprise the silicon oxide material and the carbon-based material. Therefore, the mass of the carbon-based material can be determined according to the mass of the silica material, for example, when the silica material is 15%, the carbon-based material can be 80-85%; for example, when the silicon oxide material is 30%, the carbon-based material may be 65 to 70%. Generally, the more the content of the silica material is, the higher the energy density can be achieved, but at the same time, the smaller the content of the carbon-based material is, the more the expansion of the silica material is intensified, the carbon-based material cannot effectively inhibit the expansion of the silica, and the cycle performance is drastically reduced. Conversely, the lower the content of the silicon-oxygen material, the higher the content of the carbon-based material, but the lower the energy density which can be achieved, the lower the endurance mileage for the new energy automobile, and the requirement of the user can not be met. The proportion of the two is controlled within a certain range, if the content of a is 5-50%, the content of b is 50-95%, and the synchronous control of the depth of discharge meets the relational expression of the invention, the energy density of the battery can be effectively improved, and the battery has better cycle performance.
In some embodiments, the carbon-based material is at least one of artificial graphite, natural graphite, hard carbon, graphene, soft carbon.
Preferably, the carbon-based material is artificial graphite or natural graphite, the silicon-based material is SiO, and the two materials are matched for useAnd is more suitable for the relational expression of the invention. Wherein, graphite is used for Li/Li + The lithium intercalation potential is about 0.1V, and the silicon is used for Li/Li + The lithium intercalation potential was about 0.4V. In the case of half-cells during charging, the positive electrode potential rises and the negative electrode potential falls (theoretical 0V), and the voltage of the full cell=positive electrode potential-negative electrode potential; the discharge is opposite to the charge, the positive electrode potential is reduced, the negative electrode potential is increased, and the negative electrode is opposite to Li/Li + The potential of the alloy is firstly beaten to 0.1V and then is 0.4V, so that the mixed system consisting of SiO and graphite mainly comprises the graphite in the early stage of lithium removal and the silicon in the later stage of lithium removal in the discharging process. In the lithium removal mode, the volume effect of the silicon lithium removal does not affect the lithium removal of the graphite lamellar structure, the lithium in the silicon is also removed as far as possible under the condition that the discharge depth under the above relational expression is met, and the expansion fracture degree of SiO particles is kept to be minimum.
In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on at least one surface of the negative electrode current collector, the negative electrode active material is disposed on the negative electrode active material layer, the negative electrode active material layer further includes a binder and a conductive agent, and a mass ratio of the negative electrode active material to the binder to the conductive agent is (90-96): (2-5): (1-5).
The negative electrode current collector may be various materials suitable for use in the art as a negative electrode current collector of a lithium ion battery, for example, the negative electrode current collector may be a metal foil or the like including but not limited to, and more particularly may be a copper foil or the like including but not limited to.
In some embodiments, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, a conductive agent and a binder, and the mass ratio of the positive electrode active material to the conductive agent to the binder is (93-98): (1-4): (1-4).
The positive electrode active material may be of a chemical formula such as Li c Ni h Co y M z O 2-b N b (wherein, c is more than or equal to 0.95 and less than or equal to 1.2, h)>0, y is more than or equal to 0, z is more than or equal to 0, h+y+z=1, b is more than or equal to 0 and less than or equal to 1, and M is selected from one of Mn and AlOr a combination of a plurality of, N is selected from a combination of one or more of F, P, S), the positive electrode active material may also be a combination of one or more of compounds including but not limited to LiCoO 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 、LiCoFSO 4 、CuS 2 、FeS 2 、MoS 2 、NiS、TiS 2 And the like. The positive electrode active material may be further subjected to a modification treatment, and a method for modifying the positive electrode active material should be known to those skilled in the art, for example, the positive electrode active material may be modified by coating, doping, or the like, and the material used for the modification treatment may be one or more combinations including, but not limited to, al, B, P, zr, si, ti, ge, sn, mg, ce, W, or the like. The positive electrode current collector may be various materials suitable for use in the art as a positive electrode current collector of a lithium ion battery, for example, the positive electrode current collector may be a metal foil or the like including but not limited to, and more specifically may be an aluminum foil or the like including but not limited to.
And the separator may be a variety of materials suitable for lithium ion battery separators in the art, for example, may be a combination of one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fibers, and the like.
The secondary battery further includes an electrolyte including an organic solvent, an electrolyte lithium salt, and an additive. Wherein the electrolyte lithium salt can be LiPF used in high-temperature electrolyte 6 And/or LiBOB; liBF used in the low-temperature electrolyte may be used 4 、LiBOB、LiPF 6 At least one of (a) and (b); liBF used in the overcharge-preventing electrolyte may also be used 4 、LiBOB、LiPF 6 At least one of LiTFSI; liClO may also be 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of them. And the organic solvent may be a cyclic carbonate, including PC, EC; chain carbonates, including DFC, DMC, or EMC; carboxylic esters, including MF, MA, EA, MP, and the like, are also contemplated. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, and control of H in electrolytes 2 At least one of an additive for O and HF content, an additive for improving low temperature performance, and a multifunctional additive.
A second aspect of the present invention is directed to an electric device including the secondary battery as set forth in any one of the above.
The electric device can be a vehicle, a mobile phone, portable equipment, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool and the like. The vehicle can be a fuel oil vehicle, a fuel gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or a range-extended vehicle; spacecraft including airplanes, rockets, space planes, spacecraft, and the like; the electric toy includes fixed or mobile electric toys, such as a game machine, an electric car toy, an electric ship toy, and an electric airplane toy; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railroad power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete shakers, and electric planers, among others.
In order to make the technical solution and advantages of the present invention more apparent, the present invention and its advantageous effects will be described in further detail below with reference to the specific embodiments, but the embodiments of the present invention are not limited thereto.
Example 1
A secondary battery comprises a positive plate, a negative plate and a diaphragm which is arranged between the positive plate and the negative plate, wherein the negative plate comprises a negative active substance, the negative active substance comprises SiO and graphite, the mass percentage of the SiO in the negative active substance is 3%, and the discharge depth of the secondary battery is S, SAnd a satisfies the relationship: s=1.015-0.5244a+0.4717a 2 About 100%.
The preparation method of the secondary battery comprises the following steps:
a) Preparation of a positive plate:
positive electrode host NCM811, conductive agent (Super P), binder (PVDF), etc. were mixed in a ratio of 97.5:1.4:1.2, adding a solvent (NMP), and uniformly stirring and mixing under the action of a vacuum stirrer to obtain positive electrode slurry; and uniformly coating the anode slurry on an anode current collector aluminum foil, and then baking, cold pressing and die cutting to obtain the anode sheet.
B) Preparing a negative plate:
mixing negative electrode main material graphite and silicon oxide (SiO) (wherein the mass fraction of SiO is a=3%, the mass fraction of graphite is b=97%), a binder 1 (PAA), a binder 2 (SBR), a conductive agent (Super P) and the like according to the proportion of 94:2.8:1.7:1.5, adding a solvent (deionized water), and stirring and uniformly mixing under the action of a vacuum stirrer to obtain negative electrode slurry; and uniformly coating the negative electrode slurry on a negative electrode current collector copper foil, and then baking, cold pressing and die cutting to obtain a negative electrode plate.
C) Preparing an electrolyte:
mixing Ethylene Carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) according to a volume ratio of 1:1:1, and then mixing the fully dried lithium salt LiPF 6 Dissolving in a mixed organic solvent according to a proportion of 1mol/L to prepare electrolyte.
D) Preparation of a diaphragm:
a 9 μm polyethylene separator was used to coat the ceramic on one side.
E) Assembling a battery:
sequentially stacking the positive pole piece, the diaphragm and the negative pole piece, enabling the diaphragm to be positioned between the positive pole piece and the negative pole piece to play a role in isolation, and then winding to obtain a bare cell; and placing the bare cell in an outer packaging shell, injecting the prepared electrolyte into the dried bare cell, and performing the procedures of vacuum packaging, standing, formation, shaping and the like to obtain the secondary battery.
According to the ratio of S=1.015-0.5244a+0.4717a 2 Calculating to obtain the secondary batteryDepth of discharge S, the secondary battery was fully charged at 0.5C and discharged at 1C to S, and the cycle performance and the degree of pulverization of SiO of the secondary battery were tested.
1) Cycle performance: the secondary battery was fully charged at 0.5C and discharged at 1C to S at 25C until the capacity of the secondary battery was decayed to 80% of the initial capacity, and the number of cycles was recorded.
2) Degree of pulverization: the secondary battery was fully charged at 25℃and discharged at 1℃to S at 0.5℃for 100 weeks, and the degree of pulverization of SiO particles in the negative electrode sheet was observed by a scanning electron microscope. The degree of pulverization ranges from no pulverization to severe pulverization and is classified into 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 in equal proportions, with greater values giving greater degrees of pulverization.
Examples 2 to 9 and comparative examples 1 to 18 were prepared by referring to the preparation method of example 1, respectively, and examples 2 to 9 were tested for cycle performance and pulverization degree of SiO according to the calculated depth of discharge S, and comparative examples 1 to 18 were properties at other depths of discharge. The results of the settings and tests for each example and comparative example are shown in Table 1 below.
TABLE 1
As can be seen from the above test results, the present invention still has better cycle performance at higher depth of discharge than the comparative examples by controlling the depth of discharge S to satisfy the relation of the present invention on the premise of the same doped SiO content. If the comparative example wants to achieve the cycle performance similar to that of the invention, the reduction of the discharge depth is needed to be achieved, and the reduction of the discharge depth can lead to the reduction of the discharge capacity and the reduction of the energy density, so that the two cannot be achieved. If the comparative example adopts a higher depth of discharge than the embodiment of the invention, not only the pulverization of SiO particles is aggravated, but also the cycle number is reduced, and the higher the SiO content ratio is, the more obvious the pulverization aggravation and the cycle life shortening are reflected.
Furthermore, as can be seen from the comparison of examples 1 to 9, siO has a certain advantage in that the pulverization degree of SiO is kept low within a certain ratio range and the cycle performance is also improved. If the SiO ratio is too high, the expansion and cracking of SiO cannot be effectively controlled, the pulverization is relatively large, and the secondary battery has higher cycle performance than other secondary batteries at the depth of discharge, but the secondary battery still cannot be used as a new energy automobile battery well, and the preferable SiO content ratio is 3-50%.
In conclusion, the secondary battery provided by the invention can maximize the discharge capacity and the cycle life on the premise of minimizing the swelling and cracking degree of SiO particles in the charge and discharge process.
Variations and modifications of the above embodiments will occur to those skilled in the art to which the invention pertains from the foregoing disclosure and teachings. Therefore, the present invention is not limited to the above-described embodiments, but is intended to be capable of modification, substitution or variation in light thereof, which will be apparent to those skilled in the art in light of the present teachings. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.
Claims (10)
1. The secondary battery is characterized by comprising a positive plate, a negative plate and a diaphragm which is arranged between the positive plate and the negative plate, wherein the negative plate comprises a negative active substance, the negative active substance comprises a silicon oxygen material and a carbon-based material, the mass percentage of the silicon oxygen material in the negative active substance is a, a is more than or equal to 3% and less than 100%, the discharge depth of the secondary battery is S, and the S and a satisfy the relation: s=1.015-0.5244a+0.4717a 2 。
2. The secondary battery according to claim 1, wherein the secondary battery is discharged to the depth of S after being fully charged at 0.05 to 3C and then discharged to S at 0.05 to 3C.
3. The secondary battery according to claim 1, wherein 3% or more and 80% or less of a.
4. The secondary battery according to any one of claims 1 to 3, wherein the silicon oxygen material is SiO x Lithium-containing SiO x SiO containing magnesium x X is more than 0 and less than or equal to 2; wherein the SiO contains lithium x The mass ratio of the lithium in the alloy is 0 to 15 percent, and SiO containing magnesium x The mass ratio of the magnesium is 0-15%.
5. The secondary battery according to claim 4, wherein the particle diameter D10 of the silicon oxygen material is 1 to 5 μm and the D50 is 4 to 15 μm; the specific surface area of the silicon oxide material is 0.8-3.5 m 2 /g。
6. The secondary battery according to claim 5, wherein the concentration of the particle diameter N of the silicon oxygen material is 0.01 to 2.
7. The secondary battery according to claim 3, wherein the mass percentage of the carbon-based material in the anode active material is b,20% or more and 95% or less.
8. The secondary battery according to claim 1 or 7, wherein the carbon-based material is at least one of artificial graphite, natural graphite, hard carbon, graphene, and soft carbon.
9. The secondary battery according to claim 1, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on at least one surface of the negative electrode current collector, the negative electrode active material is provided on the negative electrode active material layer, the negative electrode active material layer further comprises a binder and a conductive agent, and a mass ratio of the negative electrode active material to the binder and the conductive agent is (90 to 96): (2-5): (1-5).
10. An electric device comprising the secondary battery according to any one of claims 1 to 9.
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| CN1610816A (en) * | 2001-12-28 | 2005-04-27 | 日本电气株式会社 | Lithium-ion secondary battery |
| CN102362384A (en) * | 2009-09-01 | 2012-02-22 | 日立车辆能源株式会社 | Nonaqueous electrolyte secondary battery |
| CN109314242A (en) * | 2016-06-15 | 2019-02-05 | 罗伯特·博世有限公司 | Cathode composition, the method and lithium ion battery for preparing cathode |
| CN114631214A (en) * | 2019-08-01 | 2022-06-14 | 株式会社杰士汤浅国际 | Nonaqueous electrolyte power storage element, method for producing the same, and power storage device |
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| CN1610816A (en) * | 2001-12-28 | 2005-04-27 | 日本电气株式会社 | Lithium-ion secondary battery |
| CN102362384A (en) * | 2009-09-01 | 2012-02-22 | 日立车辆能源株式会社 | Nonaqueous electrolyte secondary battery |
| CN109314242A (en) * | 2016-06-15 | 2019-02-05 | 罗伯特·博世有限公司 | Cathode composition, the method and lithium ion battery for preparing cathode |
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